Make isMod a virtual method so it can be called from the base class too

src/twitch/twitchchannel.cpp

@@ -90,7 +90,7 @@ void TwitchChannel::sendMessage(const QString &message)
     singletons::IrcManager::getInstance().sendMessage(this->name, parsedMessage);
 }
 
-bool TwitchChannel::isMod()
+bool TwitchChannel::isMod() const
 {
     return this->mod;
 }

src/twitch/twitchchannel.hpp

@@ -22,7 +22,7 @@ public:
     bool canSendMessage() const override;
     void sendMessage(const QString &message) override;
 
-    bool isMod();
+    bool isMod() const override;
     void setMod(bool value);
     bool isBroadcaster();
     bool hasModRights();